Our research indicates that this arrangement actually does not improve passenger safety in a high speed vehicle crash in which forward motion of the vehicle is rapidly decelerated, such as an aircraft crash. We have found that in such a crash the first contact of a passenger thrown forwardly against the backrest of the seat in front is likely to be with the knees and/or hands and that the force thereby applied, together with the inertia of the backrest itself, is likely to be sufficient to cause it to break forwardly. That creates a larger space in which the head of the passenger can move forwardly with acceleration. The backrest will be stopped by striking a passenger (if present) occupying that seat in front or on reaching the end of its possible travel and there will then be a much more severe impact when the passenger's head strikes the backrest. We believe that the creation of that larger space and the resultant acceleration of passengers' heads is the cause of many head injuries in survivable crashes. This invention aims to reduce or eliminate that space.